Oxidative Carbonylation Of Ethanol Research Articles

Synthesis of Diethyl Carbonate in Liquid Phase Oxidative Carbonylation over Activated Carbon-Supported Chloride-Free Cu-Based Catalysts

Synthesis of diethyl carbonate (DEC) in the liquid phase by oxidative carbonylation of ethanol over activated carbon (AC)-supported chloride-free Cu-based catalysts offers a prospective “green chem...

PdCl2-loading mesoporous copper oxide as a novel and environmentally friendly catalyst for diethyl carbonate synthesis

PdCl2-loading mesoporous copper oxide (PdCl2/mCuO) catalysts were successfully synthesized via a hard template with copper carbonate basic (Cu2(OH)2CO3), cupric nitrate (Cu(NO3)2·3H2O) and copper citrate (Cu2C6H4O7·2.5H2O) as the copper(II) precursors, respectively. Their catalytic performances were investigated in the synthesis of diethyl carbonate (DEC) by oxidative carbonylation of ethanol with CO and O2. The catalysts were characterized by TGA, XRD, nitrogen adsorption–desorption analysis and SEM with the aim of establishing their composition, morphology and structure. It was observed that the catalysts all showed a good selectivity to diethyl carbonate. However, due to a better mesoporous structure such as a bigger surface area, more uniform particle size and less agglomeration, the PdCl2/mCuO-1 catalyst prepared with Cu2(OH)2CO3 precursor showed a better catalytic activity that the conversion of EtOH was about 4.8% and the STY of DEC was 97.1mgg−1h−1. This was because the highly developed mesoporous structure could generate a bigger surface area, which benefited the contact between reactants and active sites, improved the conversion of ethanol, and thus enhanced the catalytic performance. Furthermore, a synthetic procedure diagram about “wet impregnation” method of mesoporous CuO prepared with Cu2(OH)2CO3 precursor was given to illustrate these results intuitively.

Enhanced CuCl dispersion by regulating acidity of MCM-41 for catalytic oxycarbonylation of ethanol to diethyl carbonate

CuCl supported on molecular sieves has attracted increasing attention in catalyzing oxidative carbonylation of ethanol to diethyl carbonate. Mesoporous MCM-41 has been widely used as catalyst support due to its large surface area and well defined mesoporous structure. Considering its intrinsic weak acidity, MCM-41 was modified by a simple impregnation method to incorporate Al. The incorporation of Al components resulted in the high dispersion of Cu species and the increase of acid sites without changing the mesoporous structure of MCM-41, and thus enhanceed the catalytic activity of CuCl/MCM-41for diethyl carbonate synthesis.

Effect of Hydrophobic Modification on the Catalytic Performance of PdCl2/Cu-HMS with Different Silylation Temperatures

A new class of organic–inorganic hybrid materials were prepared by combining Cu-HMS with a silylation agent, trimethylchlorosilane (TMCS) via a simple silylation process at different silylation temperatures. They were characterized by a series of techniques including FT-IR, powder XRD, Nitrogen adsorption–desorption, TG analysis and water adsorption capacity test. It was demonstrated that silylation of PdCl2/Cu-HMS catalysts with TMCS enhanced their hydrophobicity, improved their activity and stability and importantly kept the excellent selectivity to diethyl carbonate (DEC) by oxidative carbonylation of ethanol in the gas-phase reaction. Moreover, the silylated samples obtained at 60 °C showed a better conversion of EtOH of 6.1 % and STY of DEC of 140.8 mg g−1 h−1.

Modification of Y Zeolite with Alkaline Treatment: Textural Properties and Catalytic Activity for Diethyl Carbonate Synthesis

In this work, we modified NaY zeolite (Si/Al = 5) with NaOH solutions of different concentrations followed by ion exchange with NH4NO3 to the H form of the zeolite. Treated NaY was used as a catalyst support for the preparation of CuY for diethyl carbonate (DEC) synthesis through the oxidative carbonylation of ethanol. The textural and acidic properties of NaY and the catalytic performance of the corresponding CuY materials were investigated. Compared with the untreated sample, CuY catalysts using modified NaY samples as supports exhibited higher conversions of ethanol and similar selectivities to DEC. Inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), N2 adsorption, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) were used to explore the origin of the improvement in activity. The experimental results showed that alkaline treatment induced defects in the zeolite framework and greatly promoted dealumination through ion exc...

Ordered mesoporous carbons supported wacker‐type catalyst for catalytic oxidative carbonylation

Ordered mesoporous carbons (OMCs) were used as supports to prepare Wacker‐type catalysts for diethyl carbonate (DEC) synthesis by oxidative carbonylation of ethanol in a gas‐phase reaction. The effect of support structure on the dispersion of the active species and catalytic properties were investigated. Nitrogen sorption, X‐ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the active components have encapsulated in pore channels of OMCs. Characterizations of the catalysts, such as TEM, scanning electron microscope (SEM) and XRD, indicated that active components supported on OMCs have better dispersion compared to activated carbon (AC). The ethanol conversion of the catalysts was improved by ∼65% using OMCs as the catalyst support than AC. The stability of the catalytic activity can also be enhanced through surface modification of OMCs. Surface oxygen‐containing groups (OCGs) on OMCs before and after surface modification were characterized by transmission IR spectra and the Beohm titration. The relationship between surface OCGs and anchor ability of OMCs was studied. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3797–3805, 2013

A novel method to reduce the influence of by-product water on the catalytic performance of PdCl2/Cu-HMS catalysts for the synthesis of diethyl carbonate

A novel method to synthesise diethyl carbonate is introduced by the coupling reaction, the hydrolysis of diethyl ether (DEE) and oxidative carbonylation of ethanol, which reduces the influence of by-product water and satisfies the energy coupling for the reaction system.

Effect of extra-framework silicon on the catalytic activity of Cuβ zeolite catalyst for synthesis of diethyl carbonate by oxidative carbonylation of ethanol

Effect of extra-framework silicon of Cuβ catalysts was investigated by oxidative carbonylation of ethanol in the gas-phase reaction. Zeolite β crystals with varying Si/Al ratio were obtained after different content aqueous NH 3·H 2O solution treatment. Cuβ catalyst with low Si/Al ratio has shown better catalytic activity for oxidative carbonylation of ethanol to diethyl carbonate (DEC). From X-ray powder diffraction (XRD), XPS, and ICP analysis, it can be concluded that the treatment of NH 3·H 2O for β zeolite facilitated selective extraction of extra-framework silicon, which produce enough room for the active center Cu +. The reaction of forming active sites for Cuβ without extra-framework silicon was studied on a molecular level using density functional theory (DFT) and transition-state theory. The reactive energy barrier of the reaction over Hβ without extra-framework silicon was lower than that with extra-framework silicon, mainly because the stereo-hindrance of SiO 2 in the support has great effect on CuCl activation. And the presence of extra-framework silicon of the support blocked the attack of Cu + to O atom. Hence, Cuβ catalyst without extra-framework silicon has better catalytic activity.

Catalytic synthesis of diethyl carbonate by oxidative carbonylation of ethanol over PdCl 2/Cu-HMS catalyst

Direct synthesis of diethyl carbonate (DEC) by oxidative carbonylation of ethanol offers a prospective “green chemistry” strategy to eliminate the phosgene used in the traditional preparation processes. PdCl 2/Cu-HMS catalyst has been investigated, which demonstrated excellent selectivity to DEC by oxidative carbonylation of ethanol in the gas-phase reaction. The Si/Cu molar ratio of mesoporous Cu-HMS supports showed a remarkable effect on catalytic activities. An optimized Si/Cu molar ratio existed for catalytic performance, which was about 50/1. From XPS, ICP, XRD, nitrogen physisorption and IR characterization and analysis, it could be concluded that copper species incorporated into HMS frame and was highly dispersed in the frame of silica. The catalytic performances of PdCl 2/Cu-HMS were related with both Cu content in the Cu-HMS and the order degree of mesoporous structure for Cu-HMS.

Effect of SSIE structure of Cu-exchanged β and Y on the selectivity for synthesis of diethyl carbonate by oxidative carbonylation of ethanol: A comparative investigation

Cu-exchanged β and Y catalysts were investigated by oxidative carbonylation of ethanol in the gas-phase reaction. Cuβ catalyst has shown better catalytic selectivity for oxidative carbonylation of ethanol to diethyl carbonate (DEC), without the principal by-product 1,1-diethoxyethane (DEE) for CuY catalysts. In order to investigate the effect of zeolite structure on the selectivity for products, computational analysis of molecular dimensions and diffusion parameters of DEC and DEE within Cuβ and CuY catalysts zeolite framework has been performed using molecular mechanics and quantum mechanics methods. The computational analysis results are in good agreement with the experimental results to some extent. DEC having a kinetic diameter of 3.663 Å and the lowest energy barrier was formed preferentially over both zeolites. However, the DEE molecule was not detected among the products over Cuβ because of its greater kinetic diameter 6.059 Å and higher energy barrier. The special architecture of β zeolite did not allow the diffusion of DEE molecules through its pores. The formation of the higher sterically hindered DEE over CuY catalyst could be explained by involvement of the outer surface.

An investigation of carbon-supported CuCl 2/PdCl 2 catalysts for diethyl carbonate synthesis

The synthesis of diethyl carbonate (DEC) by the oxidative carbonylation of ethanol was investigated using catalysts prepared by the dispersion of CuCl 2 and PdCl 2 on amorphous carbon promoted with KCl and NaOH. Catalysts were characterized extensively by XRD, XAFS, SEM and TEM with the aim of establishing their composition and structure after preparation, pretreatment, and use. It was observed that after preparation and pretreatment in He at 423 K copper is present almost exclusively as Cu(I), most likely in the form of [CuCl 2] − anions, whereas palladium is present as large PdCl 2 particles. Catalysts prepared exclusively with copper or palladium chloride are inactive for DEC synthesis, indicating that both components must be present together. Evidence from XANES and EXAFS suggests that the DEC synthesis may occur on [PdCl 2− x ][CuCl 2] x species deposited on the surface of the PdCl 2 particles. As-prepared catalysts exhibit an increase in DEC synthesis activity and selectivity with time on stream, but then reach a maximum activity and selectivity, followed by a slow decrease in DEC activity. The loss of DEC activity is accompanied by a loss in Cl from the catalyst and the appearance of paratacamite.

The effects of promoters over PdCl2-CuCl2/HMS catalysts for the synthesis of diethyl carbonate by oxidative carbonylation of ethanol

Diethyl carbonate (DEC) has been produced by the oxidative carbonylation of ethanol in the gas phase over a heterogeneous PdCl2-CuCl2 catalyst supported on hexagonal mesoporous silica (HMS). The various quaternary ammonium salt (QAS) promoters have a great effect on the performance of the catalyst, which was due to the high dispersal of the active species on the film composed of nonpolar groups. The catalytic performance of the PdCl2-CuCl2/HMS catalyst was greatly improved by the addition of promoter tetraethyl ammonium bromide (TEAB). Under the PdCl2-CuCl2-TEAB/HMS catalyst system, space time yield (STY) of DEC was 210.9 g DEC/(L-cat h), and conversion of EtOH was 13.6%. An optimized TEAB/Pd mole ratio existed for catalytic activity, which was about 12/1. From X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low-temperature electron spin resonance (ESR) spectroscopy, and infrared resonance (IR) spectroscopy, it could be concluded that the essential role of TEAB not only promoted the formation of surface-stabilized copper species but also improved a high dispersal of the active species, which enhanced catalytic performance in the gas phase DEC synthesis.

A new type of catalyst PdCl 2/Cu-HMS for synthesis of diethyl carbonate by oxidative carbonylation of ethanol

A new type of catalyst, PdCl 2/Cu-HMS, for diethyl carbonate (DEC) synthesis by oxidative carbonylation of ethanol in the gas-phase reaction was investigated. The modified support Cu-HMS which was synthesized using the neutral templating pathway at the room temperature kept its mesoporous structure even after it was calcined repeatedly at 550 °C for 3 h to remove the template. From XRD, XPS and ICP analysis, it can be concluded that copper incorporated into HMS frame and was highly dispersed in the frame of silica. Notably, the degree of order of mesoporous molecular sieves was improved in a certain extent after PdCl 2 was loaded on Cu-HMS samples. The PdCl 2/Cu-HMS catalyst exhibited excellent selectivity for DEC. The catalytic reaction mechanism was illuminated by the interaction between Pd 2+ loaded on the surface and Cu 2+ in Cu-HMS frame.

Production of diethyl carbonate from ethanol and carbon monoxide over a heterogeneous catalytic flow reactor

Diethyl carbonate (DEC) is a candidate for use as an oxygen-containing additive in gasoline and diesel fuel to diminish pollutant emissions. The synthesis of DEC by the oxidative carbonylation of ethanol in the gas phase over heterogeneous CuCl 2/PdCl 2 catalysts supported on activated carbon (AC) has been investigated using a laboratory-scale continuous flow reactor with online GC/MS. Influences of various reaction conditions and catalyst pretreatment on the DEC yield and selectivity have been tested. Yield of DEC at 150 °C reached a maximum of 12.5 wt.% and was found to increase with an increase of residence time, reaction temperature, and reaction pressure as expected. The relationship between CO flow rate and production of DEC showed three distinct regions of DEC production. A by-product, diethoxymethane (DEM), was formed when ethanol was introduced in stoichiometric excess. Catalyst pretreated with KOH presented the best catalytic performance, and all metal hydroxides tested enhanced the yield of and selectivity for DEC simultaneously. However, the CuCl 2/PdCl 2/AC–KOH catalyst with a higher OH/Cu mole ratio than 2.0 showed an even lower DEC yield than that found using a CuCl 2/PdCl 2/AC catalyst without KOH.

Production of Diethyl Carbonate from Ethanol and Carbon Monoxide over a Heterogeneous Catalyst

Diethyl carbonate (DEC) has been produced by the oxidative carbonylation of ethanol in the gas phase over a heterogeneous CuCl2/PdCl2 catalyst supported on activated carbon. Yields of DEC with this catalyst are approximately 10 wt % with the byproducts diethoxymethane, ethyl formate, and acetaldehyde also formed in significantly lower yields. Treatment of the catalyst immediately after preparation with potassium hydroxide enhances the production of DEC almost 2-fold without increasing the amount of byproducts formed. The reactions that form DEC and the byproducts occur in a parallel, rather than a sequential, manner indicating that it should be possible to identify a catalyst which is more selective for DEC.